Abstract:
Lake Victoria is famous for its in evolutionary terms young but species-rich assemblage of cichlid fishes. This superflock also includes additional
species from adjacent water systems. Lake Victoria is surrounded by several smaller lakes that are connected to the main water body of Lake
Victoria only through swampy areas. Lake Kanyaboli is one such lake, harbouring a much poorer species diversity, mostly comprised of Lake
Victoria endemics, some of which are now considered extirpated from the main lake. The focus of this study was on the modern haplochromine
component of the cichlid fauna, represented by Lipochromis maxillaris, Astatotilapia nubila, Xystichromis phytophagus and Astatotilapia sp.
Bigeye, as well as a number of morphologically distinct haplochromine specimens that could not be assigned to any of the recognized species. We
used five microsatellite markers to distinguish these five taxa. Genetically, L. maxillaris was clearly differentiated from all other taxa, and
A. sp. Bigeye was moderately differentiated from the remaining three. Astatotilapia nubila, X. phytophagus and the unidentified specimens
constituted a partially overlapping cluster. As each of the clusters had several (5–14) private alleles, extremely recent divergence is suggested. As
all taxa except for A. sp. Bigeye and the unidentified specimens also occur or at least occurred in Lake Victoria, it is likely that they evolved as
part of the Lake Victoria superflock, while A. sp. Bigeye and the unidentified specimens may have currently evolved in situ. The observation of
slightly distinct albeit overlapping body shapes and the extremely close genetic relationship between three of the five taxa are fully compatible and
in support of the hybrid swarm theory of adaptive radiation.
